Boiler displays E11; flue gas temperature is too high.

Safety: Turn off power and gas. Do not operate the boiler with a known flue gas overtemperature condition.

• Step 1 – Inspect venting: Check the entire vent run for blockages, sagging, or improper slope that could trap condensate. Ensure terminations are clear outside.
• Step 2 – Check condensate drainage: Verify that the condensate trap and drain line are clear so condensate can leave the heat exchanger. A flooded exchanger can cause abnormal flue temperatures.
• Step 3 – Visual check of the heat exchanger: With the burner removed (by a professional if necessary), inspect the stainless steel heat exchanger for heavy scale or soot. Cleaning requires proper tools and should be done by a technician.
• Step 4 – Sensor inspection: Locate the flue gas temperature sensor on the flue outlet of the Triangle Tube boiler. Ensure it is firmly mounted and the wiring is intact.
• Call a technician: Flue gas overtemperature often indicates combustion or scaling issues. A licensed technician must perform combustion analysis, clean the heat exchanger, and replace the flue gas sensor if needed.